(a) Field of the Invention
The present invention relates to a photographic camera and, more particularly, to an apparatus and a method for preventing the deviation of a focal plane shutter blade.
(b) Description of the Related Art
A focal plane shutter, which comprises two sets or curtains of shutter blades each having a plurality of opaque thin plates, is installed in front of a photographic film surface. The two curtains include a leading blade curtain and a trailing blade curtain. During a film exposing operation, the leading blade curtain is moved from an extended state to a contracted state, whereupon the trailing blade curtain is moved from a contracted state to an extended state. A shutter speed is determined on the basis of the duration and width of a slit between the leading blade curtain and the trailing blade curtain.
A leading blade curtain 12 of a focal plane shutter appears when a back cover is opened, as shown in FIG. 1. When a user loads a film cartridge 15 in a cartridge chamber 11 and winds it onto a spool 13, the user may mistakenly touch the leading blade curtain 12 so that the focal plane shutter (leading blade curtain) may deviate from an initial position. The deviation of the focal plane shutter blade causes errors in photographic operation.
A conventional camera has a focal plane shutter attached to a sensor for detecting the deviation of the focal plane shutter, so that a release switch locks when the sensor detects the deviation. However, the conventional camera merely detects the deviation, but does not prevent such deviation from occurring.